Quick! First thought when you see this picture?

Nope, you're wrong. That's the Mercury 7, baby.

NASA - The Original Seven:

"In this 1960 photograph, the seven original Mercury astronauts participate in U.S. Air Force survival training exercises at Stead Air Force Base in Nevada. Pictured from left to right are: L. Gordon Cooper, M. Scott Carpenter, John Glenn, Alan Shepard, Virgil I. Grissom, Walter Schirra and Donald K. Slayton. Portions of their clothing have been fashioned from parachute material, and all have grown beards from their time in the wilderness. The purpose of this training was to prepare astronauts in the event of an emergency or faulty landing in a remote area."

Hat tip Warren Ellis.